#include <iostream>
using namespace std;

void get_lost_number(int data[], int length)
{
	int index;

	unsigned char* pFlag = (unsigned char*)malloc(length * sizeof(unsigned char));
	memset(pFlag, 0, length * sizeof(unsigned char));

	for(index = 0; index < length; index++){
		if(0 == pFlag[data[index]])
			pFlag[data[index]] = 1;
	}

	for(index = 0; index < length; index++){
		if(0 == pFlag[index])
			printf("%d\n", index);
	}

	free(pFlag);
	return;
}

